Information storage arrangement employing circulating memories



T. R. PETERS 3,387,281

INFORMATION STORAGE ARRANGEMENT EMPLOYING GIRCULATING MEMORIES June 4, 1968 3 Sheets-Sheet 1 Filed Nov. 12, 1965 //VI/EN 7'OR T. R. PETERS T. R. PETERS June 4, 1968 INFORMA'IION STORAGE ARRANGEMENT EMPLOYING CIRCULATING MEMORIES 3 Sheets-Sheet 2 Filed Nov. 12, 1965 June 4, 1968 1. R. PETERS 3387231 INFORMATION S'I'ORAGE ARRANGEMENT EMPLOYING CIRCULATING MEMORIES Filed Nov. 12, 1965 5 Sheets-Sheet 5 CONNECT/NG 84, CLOCK 8 5 z Ccr B/NARY cowv TER C CONNECT/NG 64/ LOCK CCT United States Patent 3387281 INFORMATION STORAGE ARRANGEMENT EM- PLOYING CIRCULATING MEMORIES Theodora R. Peters, Flanders, N.J. assignor to Bel! Telephone Laboratories, Incorporatetl, New York, N.Y. a

corporation of New York Filet! Nov. 12, 1965, Ser. No. 507,447 19 Claims. (Cl. 340-172.5)

This invention relates to data processing arrangements and, more specifically, to a data storage organization for closely packing digital information in a circulating memory.

Memories used in data processing systems may be divitled into three classes, according to their respective ac eens proporties. In a random access memory, storage locations can be interrogated in any order, with each readout requiring an equal time interval. Magnetic cores, thin ferromagnetic films and twister wires comprise illustrative storage elements for random access memories.

In addition, there are two data circulating memories, viz. periodic access and sequential access arrangements. In the periodie access configuration, access time to any memory location is variable, depending upon the time interval sinee the location was last available for data outpntting. Correspondingly, in a sequential access store, a reaclout frorn successive or adjacent memory locations is the only interrogaon desired, with each readout taking an equal time period. Rotating magnetic drums or discs, and recirculating delay lines are examples of recirculating memories.

When digital information is supplied on an asynchronous basis for storage to, or read out from what is functionally a recirculating memory, prior art arrangements have heretofore ernbodied such recirculating operationai structures with typical random access memory configurations, and utilized these devices in a restrictive way, eg, aceessed by binary counters to seqnentially interrogate contiguous storage locations. Since random access memory structures are con iderably more expensive per bit of storage than recirculating organizations, typically by an order of magnitude, and also characterized by a relatively slower access time, snch prior art arrangements have been found seriottsly deficient.

It is therefore an object of the present invention to provide an improved digital storage arrangement.

More specifically, it is an object of the present invention to provide a relatively inexpensive recirculating memory which may advantageously receive data trom, or supply data te asynchronousiy operated circuit elements.

It is another object of the present invention to provide a relatively inexpensive sequential memory organization which exhibits a relativeiy fast access time.

These and other objects of the present invention are realized in a specific iilustrative storage organization for closely packing asynchronously supplied input data in a sequential access memory. The arrangement comprises a plurality of eascaded periodic memory stages of diterent periodicities to connect a data input source to the sequential memory. An integral or common multiple relationship characterizes the relative capacities of the memories, such that each storage arrangement is sequentially enabled to fill the next larger stage.

In addiiion, the above-deseribed arrangement in inverted form may be employcd to provide an interface between a sequential access memory and an asynchronous data output element.

It is thus a feature of the present nvention that a recirculating information storage arrangement comprise a principal recirculaling memory and a plurality of synchronized periodic memory stages cascaded therewith.

It is another feature of the present inventon that a Patentecl June 4, 1968 recirculating information storage arrangement comprise an asynchronous data source, a circulating memory characterized by a capacity of m bits, and a plurality of cascaded intermediate storage stages connecting the source and the circulating memory, with each of the intermediate storage stages comprising a plurality of like periodic memories of capacity m/n, where m, u and m/n are positive integers.

A complete understanding of the present invention and of the above and other features, advantages and variations thereof may be gained from a consideration of the following detailed description of an illustrative embodiment thereof presented hereinbelow in conjunctin with the accompanying drawing, in which:

FIG. 1 is a schematic diagram depicting the data processing portion of an illustrative data storage organization which embodies the principles of the present invention;

FIG. 1A is a side view of a drum 30 shown in FIG. 1 illustraling the circuitry associated therewith;

FiG. 2 is a diagram illustrating the control circuitry for three magnetic drums 30, 34 and 40 shown in FIG. 1;

FIG. 3 illustrates the control cireuitry associnted with two digital registers 20 and 21 and a magnetie drum 30 shown in FIG. 1; and

FIG. 4 is a diagram depicting a data outputting organization which embodies the principle-s of the present invention.

Referring now to FIG. 1, there is shown a specific i1- lustrative data storage arrangement for closely paeking data asynchronously supplied by an input source 10 in a circulating memory 50. Closely packing defines a mode of data storage wherein consecutive bits of information are registered in contiguous storage cells in a digital memory, e.g. in the element 50. Cascaded between the source 10 and the principal memory are three intermediate data storage stages respectively comprising, frorn left to right, two shift registers 20 and 21, two periodic memories 30 and 34, and two additional periodic memories 40 and 44. It is noted that the memories 30, 34, 40, 44 and 50 may be ernbodied by any eirculating storage arrangement, and will henceforth be treated as comprising rotating magnetic drums. While only one track for the drums 30, 34, 40, 44 and 50 is shown in FIG. l, these drums inelude a plurality of parallel tracks inclucling one control track, and an addtional track for each bit in the digital words to be processed. Similarly, there are plural shift registers 20 and 21 in one-to-one correspondence with the bits in the input words. The multitrack nature of a typical ruagnetic drum, viz, the drum 30, is shown in detail in FIG. 1A.

A plurality of data writing heads 31W, 35W, 41W, 45W, and 51W, and a plurality of reading heads 31R, 35R, 41R, 45R, and 51R are respectively coupled to the drums 30, 34, 40, 44 and 50. Also, a plurality of data links 25, 26, 27, 32, 37, 38, 42, 47, and 48 are employed in the FIG. 1 arrangement to selectvely connect the magntic drums and the shift registers. In particular each data storage element in a given stage is adapted to selectively supply dgital information to the upper drum in the following stage. Also, the upper memory in any stage is further selectively operable to pass data to the lower memory in the same stage. In this regard a pluralty of normally open relay contacts A through I are included in the interstage and intrastage links to control the flow of information between storage devices. The relay contacts A through I are shown in the wellknown detached contact form, and are controlled by circuitl'y generally illustratcd in F168. 2 and 3. It is 0bservcd that all structural items first identified in this paragraph, i.e. the writing and reading heads, the interand intrastage memory-connecting links, and the contacts A through I are multiply ineluded in the instant arangement once for each parallel control and/or data track. This multiplicity of circuit elements is depicted in FIG. 1A for components associated with the drum 30.

The asynchronous input data source 10 is connected to the input of the register 20 via a data lead 11, and further connected to each stage of the registers 20 and 21 by a set of control leads 12. The leads 12 are energized by the source 10 whenever the source impresses data on the lead 11. Further, an output circuit 80 is connected to the reading head 51R coupled to the principal circulating memory 50. It is again observed that there are plural leads connecting the source 10 to the registers 20 and 21, and connecting the memory 50 to the output circuit 80 in one-to-one correspndence With the number of parallel data tracks.

Finally, the data processing portion of the instant arrangement ineludes a write mark generator 28 for connecting two interstage links 26 and 27 to the drum 30, as illustrated in FIGS. 1 and 1A. The element 28 may advantageously comprise circuitry similar to that shown in A. A. Cohen et al. Patent 2,614,169 issued Oct. 14, 1952, or that disclsed in W. E. Baker et al. Patent 3,107,- 344 issued Oct. 15, 1963, and is functonally adapted to place a single binary 1" dgit in the control track of the drum 30 in a storage location corresponding to the first empty storage cel] in the drum 30 data tracks following each data entry in the drum 30. Moreover, the generator 28 is further operable to translate data bits from the registers 20 and 21 to the first data track in the drum 30. Alternatively, the element 28 may embody a delayed pulse generator which is operable in response to a closure of the contact B or C in the lead 26 or 27.

The digital capacity of each storage stage (per parallel data track) bears an integral devisor relationship to the capacity of the principal circulating memory 50, and is dependent upon both the bit time spacing between contigu0us addresses in the memory 50 and also upon the maximum input data rate for the asynchronous input source 10. For purposes of concreteness, and without any loss of generality, assume that the principal memory 50 has a capacity per track of 1028 hits with a bit spacing of microseconds, i.e., one bit can be written into the memory 50 every 10 sec. Assume further that the input source 10 supplies at most one word every 80 sec. Accordingly, many input words are typically supplied by the source 10 before the desired, first empty storage address in the memory 50 is coupled to the associated writing head 51W. Moreover, since the input source 10 is not synchronized with the memory 50, there can be no direct data translation connection therebetween even if speed were not a factor. Hence, the intermediate storage stages are required to provide a buffering interface between the input source 10 and the memory 50.

With respect to the data capacity of the several memory devices employed in the FIG. 1 organization, assume (worst case) that the drum 50 storage cell which is to be next accessed has just passed by the writing head 51W. This address wil] next be coupled to the writing head 51W in Q sec bit (1) During this time, the input source 10 can supply at most 1024 words X =10.24 milliseconds one word every 80 usec., or a total of 1 Word 0 10...4 meer). sec- -128 V\0rds the principal memory 50 bit spacing, i.e. (1.SCC. versus 10 uSGC.

Similarly, assuming that the drum 40 has just rotated the next address to be accessed by a middle buifer stage drum past the associated writing head 41W, this desired memory cell will next be coupled to the head 41W in bit (3) During this time interval, the input source 10 can supply at most 128 words =1.28 msec.

Because of this small capacity, shift register storage is more economical than a two-bit magnetic drum. Therefore, the input buffering stage compnses the two shift registers 20 and 21 each including two storage locations.

The integral capacity ratio charracterizing contiguous storage stages give rise to a requirement for two storage elements (drums or shift registers) in eaeh bufiering stage. More specifically, each intermediate storage stage rotates eight times for one complete eycle of the following stage and, moreover, is selectively operable to fill oneeighth of the next following stage. Thus, when the top butler memory of a stage is full, but the first empty oneeighth sector of the upper following stage memory is not coupled to the corresponding drum writing head, the full memory must empty its contents into its associatecl, likesize memory in order to accommodate information whioh may be directed thereto from the previous buifering stage.

The information flow between any two contiguous memory stages is regulated by the leads 25, 26, 27, 32, 37, 38, 42, 47 and 48, the contacts A through I, and the controlling arrangements of F168. 2 and 3, discussed hereinafter, in accordance with the following set of rules:

(l) Never read information out of any buffer memory until it is full, unless the data input cycle has ended, at which time all buffers are to be sequentially emptied;

(2) An upper storage element places its contents into the upper memory of the following stage if the first empty one-eighth sector of that drum is coupled to the associated drum Writing head at the time the previous stage memory becomes full. If the following stage drum is not so oriented, write from the upper memory into the lower memory of the same stage;

(3) Empty a full lower memory into the next stage upper memory when the proper one-eighth sector of the larger memory is coupled to the associated drum writing head; and

(4) After the data input cycle has endeci, translate all information contained in all partially full intermediate memories in a left-to-right direction, emptying such memories in a left-toright bottom-to-t0p order.

In accordance with the above rules, the FIG. 1 data storage arrangement functions in the following manner. At the inception of a data input cycle, each of the buffer registers and memories is initially empty. Moreover, the drums 30, 34, 40, and 44, and the memory 50 are synchrronized in the sense that the control tracks on the drums each contain an nitial, single binary 1 write here mark which are coincidentally coupled to the respective drum reading heads once for each cycle of the memory 50. That this synchronization is possible directly follows from the integral 8 to 1 capacity relationship charactorizing the memories in contiguous storagc stages.

The first two infurmation words supplicd by the source 10 to the input lead(s) 11 during n data writing cycle are inserted into the register under control of the concidentally energized control leads 12. At the time the second information word is so supplied, pursuant to the first three rules given above, the full (2 bits) register 20 must be empticd into cither the drum or the lower input stage register 21. If the write here control mark on the drum 30 control track is detected at the associated drum reading head 31R when the second input word is produced by the source 10, hence indicating that the first one-eighth sector of the drum 30 is available for data inputting, the contents of the register 20 are translated to the drum 30. At the same time, the nitiai write here mark in the control track of the drum 30 is shifted two bit spacings by the mark generator 28 to indicate where the next information bits are to be placcd, This data flow is effected by a closure of the contacts C (F168. 1 and 1A) by the FIG. 3 control circuitry considered hereinafter.

Correspondingly, if the drum 30 is not so oricnted at this time, the contacts A are closed, and the two information bits flow into the register 21. The data remains in the register 21 untii the drum 30 rotates to the proper data receiving position, which is detected by the control circuitry whcn the drum 30 reading head 31R detects the bnary 1 write here digit in the control track. The information is then translated between the register 21 and the data tracks of the drum 30 via the contacts B. 11 is noted that at most .16 miliisec0nd can eiapse until the drurn 30 attains an nformationreceiving status and, during this period, thc source 10 can suppiy at most two input words. These data words may bc directly inserted in the now empty upper input stage register 20.

The above-described mode of data processing continues eight times until the drum 30 is completely filled With information. At such a time, the drum 30 is in a functi0nal state identically analogous to the aforediscussed ull status for the input stage upper register 20. More particulariy, the filled drum 30 will write -riirectly into the first empty one-eighth sector of the middle stage upper drum if the vurite here mark on the control track of the drum 40 is then coupied to the corresponding readng head 41R. The write here mark in the drum 40 is automatically shifted to the proper position when the contents of the drum 30 control track are written therein. If the drum 40 is not so rotationaily oriented, the full drum 30 writes into the lower middle stage drum 34 which retains the information untii the proper oneeighth sector of the foilowing stage memory 40 is accessibie.

The above circuit functioning continues untii the drum 30 has, in turn, been fiiled eight times by the input stage registers 20 and 21. Following tl'1is, all eight sectors of the upper middle stage drum 40 are filled, and the memory 40 writes into the principie crcuiating memory 50, or into the drum 44 depending on whetirer or not the first onc-eighth sector of the memory is available at the writing head 51W, as determined from the position of the write here mark on the control track of the memory 50. Again, the above information processing recurs until the drum 40 has been fiiled by the drums 30 and 34 eight times, at which point the principai memory 50 is completeiy filied. This ends an information inputting cycle, and the stored data may be read from the memory 50 by the output circuit 80 via the reading head 51R on either a sequential or a periodc basis, 21s desired For the above-considered circuit functioning, it was assumed that the input source 10 supplied suflcient data to compietely fill the principal memory 50 during a data inputtng time interval. lf this is not the case, the FIG. 1 storage arrangement is constrained by the associ ated control circuitry illustrated in FIGS. 2 and 3 to translate all the data which has been generated by the source 10 to the memory 50 after the write cycle terminates. More specifically all partially fuil buffer memories are sequentially emptied in a ieftto-right bottom-to-top order until all available information has been closely packed in the memory 50. Then, as before, the now par tiaily fiiled memory 50 may be interrogated by the output circuit in a periodic or sequential manner.

Thus, the FIG. 1 arrangement has been shown by the above to accept data asynchronously supplied by the source 10, and to closely pack this information in the circulating memory 50.

An illustrative circuit arrangement for controlling a typical related set of connecting link contacts, i.e., the contacts D, E, and F between the mdclle and final buffering stages, is shown in FIG. 2. The arrangement comprises control information relating to the status of the data supplying stage memories, the status of the upper memory in the receiving stage, and the status of both memories in the preceding stage. This control information is respectively contained in the control tracks of the drums 30 and 34, the control track of the receiving drum 40, and in the state of a two-stage binary counter 15, which is advanced by pulses appearing on the input control lead 12. With respect to the counter 15, it is noted that the binary signals appearing at two output terminals 16 and 17 thereof selcctively indicate whether or not data is presently stored in the registers 20 and 21.

A clock source 84 is included in the FIG. 2 arrangement and includes an output terminal 85 thercon which is continuousiy energized foliowing the end of each write cycle. In addition, a connecting circuit 71 is adapted to receive digital control information from the clock output terminal 85, the two counter 15 output terminals 16 and 17, and the reading heads 31R, 35R and 41R which are respcctively coupled to the control tracks of the drums 30, 34 and 40.

The connecting circuit 71 is a combinatoric logic arrangement which responds to a plurality of Boolean input variable in accordance With three output Booiean functions for selectively operating the switch contacts, D, E, and F shown in FIG. 1. More specifically, the contacts D, E, and F are ciosed when the corresponding combinatoric function shown below the circuit 71 in FIG. 2 is satisfied, wherein the Boolean variables represcnted by lower case letters in the functions corrcspond to sgnals whose source is identified by a like letter elsewhere in FIG. 2. Thus, for exampie, the Boolean variablcs m, 11 and 0 respectively identify binary signals which appear at the reading heads 31R, 35R and 41R coupled to the control tracks of the drums 30, 34 and 40. The circuit 71 may advantageously comprise any well-known combinatoric embodiment, such as electronc switching circuitry of the relay structures shown in chapter 4 of a text by S. H. Caldwell entitled Switching Circuits and Logical Design, copyrighted in 1958 by John Wiley & Sous, Ine.

The Boolean functions D, E and F shown in FIG. 2 operate the corresponding contacts D, E and F in accordance With the ruies and illustrative examples given ubove. The first expression in each function corresponds to a contact closure during the write cycle when data is still forthcoming from the source 10, while the second expression gives rise to a completed data path after the write cycle ends when all partially filied memories are sequentially emptied into the larger storage stages.

For example, the closure of the interstage contacts D is determined by the Boolean function m o+z 55 0 7 W. The first expression is a. "1 resulting in a closure of the contacts D, when the write here digt on the control track of the drums 30 and 40 are coincidentaliy couplcd to the rcspective reading heads 31R and 41R(m and 0), thus ndicating that the drum 40 is in a position to accept data while the drum 30 is full and therefore waiting to transmit information, and also when the drum 34 is not full and hence not in a data transrnitting state. It is observcd that the variables m, n and 0 attain dgital 1 or 0" vulues when the write hete con- 7 trol marks are, or are not coupled to the respective reading heads 31R, 35R and 41R.

In addition, the second expression in the above Boolean function, viz, 2 7 K is a 1, and results in a closure of the contacts D, if the data inputting cycle has ended (z), and the binary counter is in the 00" state (j and indicating that the registers and 21 have already been emptied and the drum 40 is oriented to re ceive information (0), ml the drum 34 is empty Hence, the composite function D shown in FIG. 2 is operable to satisfy all the rules set forth above for proper functioning of the contacts D included in the F1G. 1 storage arrangement. Correspondingly, the Boolcan functions E and F shown in FIG. 2 likewise satisfy the requirements for proper circuit operation of the FIG. 1 een tacts E and F.

The control structure for selectively interconnecting the buffering magnetic drums 40 and 44 and the principal memory 50 is essentially identical to the organization shown in FIG. 2, and will not be considered further herein. The structure for regulating the data flow between the input bulering stage registers 20 and 21, and the drum 30 is shown in FIG. 3. An analysis paralleling that given above illustrates that the Boolean expressions for A, B, and C shown in FIG. 3 operate the corresponding FIG. 1 contacts A, B, and C in a marmer to produce the desired data translation.

It is noted at this point that the operational rules emumerated above, together with the control circuitry for operating the storage arrangements in conformity with these rules, comprise only one of a plurality of possible modes of operation for the buffer memories and the principal circulating memory 50 shown in FIG. 1. Per example, the leads 27, 37, and 47, together with the contacts C, D, and I respectively included therein, may be deleted from the FIG. 1 arrangement. In such an organization, data always fiows from a full upper stage memory into the lower memory of the same stage, and then into the upper memory of the next stage. The attendant control structure is accordingly simplified since data always follows a like path, but the operational speed for the composite system is diminished. However, in any mode of operation, and independent of the particular control circuitry embodying the underlying operational ruies, a plurality of synchronized buter memory stages, including a plurality of memories hearing an ntegral or a common multiple capacity relationship are employed. It is noted that where a common multiple, rather than an integrai capacity relationship is utilized, the control logic structure is increased in complexity, since memories in contiguous stages are mutually oriented for data translation only once during a piurality of rotations of the larger device.

The discussion hereinabove was principally directed to the circuit arrangement shown in FIG. 1 for connecting the asynchronous data source 10 to the principal circulating memory 50. Turning now to FIG. 4, there is shown a corresponding arrangement for connecting the principal memory 50 to an output circuit 90 which aceepts data on an asynchronous basis. The arrangement is essentially the mirror image of the l-IG. 1 structure, with left and right, and top and bottom being reversed. The structural correspondence between the elements included in the arrangements of FIGS. 1 and 4 is indicated by the unprimed and primed reference numerals respectively shown in the two figures. The data outputting organization of FIG. 4 operates in a manncr directly inverse to the above description for the FIG. 1 systcm. with a closely packed principal 0r buffer memory sequcntially unloading adjacent one-eighth scctors into a right adjacent smaller storage device. Subject to the above enumerated inversions, the aforegiven circuit description for the F1G. 1 arrangement is equally descriptive of the FIG. 4 data translation organization. Hencc, no further discussion is (lirccted thereto.

It is observed at this point that while two memories were included in each buffering stage in the FIG. 1 arrangement, any number might well have been cmployed, With data links selectively connecting the storagc devices in each stage to each other and to the next buttering stage. The number of required stages is decreased as the number of memories per stage is increased, but the requisite control structure is increased in complexity.

Finally, it is noted that the number of bultering stages can also be truncated by making the periodic memories in any buftering stage shift registers, and directly connecting the input source 10 of F1G. 1 thereto While deleting all stages to the left thereof, i.e., all stages with smaller memories. For example, the registers 20 and 21 may be eliminated, and the drums 30 and 34 each replaced by a 16 bit shift register. The resulting buffering array wil] then function in a manner identically paralleling that given above for the FIG. 1 storage organization, with the 8 to 1 storage capaeity ratio between contiguous buffering stages being preserved.

T0 summarizc, an illustrative storage arrangement for closely packing asynchronously supplied input data in a sequential access memory comprises a plurality of cascaded periodic memory stages of different periodicitics to connect a data input source to the sequential memory. An integral or common multiple relationship characterizes the relative capacities of the memories such that each storage arrangement is sequentially enabled to lil] the next larger stage.

In addition, the abovedescribed arrangement in invertcd form may be employed to provide an interface between a sequential access memory and an asynchronous data Output element.

It is to be understood that the abovedescribed arrangements are only illustrative of the application of the principles of the present invention. N'umerous other arrangements may be devised by those skilled in the art without departing from the spirit and scope thereof. For example, an interface between unsynchronized, asynehronous input and output sources may be effected by combining the arrangements shown in FIGS. 1 and 4.

Also, it acoustical delay lines are employed in place of the magnetic drums in the FIG. 1 Organization, bit spacings of the order of nanoseconds may be obtained.

What is claimed is:

1. In combination, an asynchronous data source, a circulating memory characterized by a capacity of m bits, where m is a positive integer, and a plurality of cascaded intermediate storage stages connectin g said source and said circulating memory, each of said intermediate storage stages comprising a plurality of like periodic memories of capacity m/rl, where n and m/12 are positive integers.

2. A combination as in claim 1 wherein the memories included in said storage stages monotonically increase in capacity trom said source to said circulating memory.

3. A combination as in claim 2 further comprising a plurality of links for selectively connecting the memories in each stage to each other and to at least one memory of a contiguous stage, and switch means serially included in said links.

4. A combination as in claim 3 further comprsing first control means responsive to any of said memories being full and to the irst available sector of an associated larger memory being oriented for data inputting for activating said switch means to connect said memories via a selected one of said links.

5. A combination as in claim 4 further comprising additional control means responsive to any of said memories being full and to the associated contiguous stage memory being not oriented for data inputting for activating said switch means to connect said full memory to another memory in the same stage via a sclectcd one of said links.

6. A combination as in claim 5 wl|cre the periodic memories included in the storage stage connected to sad data source comprise shift registers.

7. A combination as in claim 6 where a plurality of said periodic memories ancl said eirculating memory includes a control track and at least one data track, and further comprising means for selectively inserting control marks in said eontrol tracks.

8. A eombinati-on as in claim 7 further eomprising output utilization means connected to said circulating memory.

9. A combination as in claim 8 further comprising a plurality of reading ancl writing heads provicling en interface between said links and said memories.

10. A eombination as in claim 9 wherein each of said memories not connected to said data source comprise rotating magnetic drums.

11. In combination, asynchronous data output means, a eirculating memory chamcterized by a capacity of m bits, where m is a positive integer, and a plurality of cascaded intermediate storage stages connecting said circulating memory and said output means, each of said intermediate storage stages comprising a plurality of like periodic memories of eapacity m/n, where n and m/ n are positive integers.

12. A combination as in claim 11 wherein said periodic memories monotonically decrease in capacity from said circulating memory to sairl output means.

13. A combination as in claim 12 further comprising a plurality of links for selectively connecting the memories included in each storage stage te each other and to at least one memory included in a contiguous stage, and switch means serially included in said links.

14. In combination, a eirculating memory eharacterized by a capacity of m bits, where m is a positive integer, and a plurality of cascadecl buffer storage stages connected to said circulating memory, each of said buffer storage stages cornprising a plurality of lke perioclic memories of capacity n, where n beurs a common multiple relation ship to m.

15. A combination as in claim 14 further comprising an input source conneeted to said buffer memories, and wherein the memories in said bulering stages monotonically increase in capacity from said input source to sact circulating memory.

16. A combination as in claim 14 further comprising output means connected to said butering stages, and wherein the memories ineluded in saicl buffering stages monotonically deerease in capacity from saicl circulating memory to said output means.

17. In eombination, an asynchronous data souree, asyn chronous data output means, a eirculating memory, 2]. first plu rality of cascadecl storage stages eonnecting saicl source and said circulating memory, and a second plurality of caseaded storage stages eonnecting said circulating mem ory :md suid output means.

18. A eombination as in claim 17 whetein said tirst and second plurality of storage stages each comprises u plural ity of like periodie memories.

19. A combination as in claim 18 wherein said periodic memories monotonically decrease in capacity in a direction away front said cireulating memory.

References Cited UNITED STATES PATENTS 2902,679 9/1959 De Phillipo et al 340174 3,013254 12./1961 Walker 340172.5 X 3,302176 1/1967 McLaughiin 340172.5

ROBERT C. BAILEY, Prmary E.ramincr.

P. R. WOOD, Asristant Examner. 

1. IN COMBINATION, AN ASYNCHRONOUS DATA SOURCE, A CIRCULATING MEMORY CHARACTERIZED BY A CAPACITY OF M BITS, WHERE M IS A POSITIVE INTEGER, AND A PLURALITY OF CASCADED INTERMEDIATE STORAGE STAGES CONNECTING SAID SOURCE AND SAID CIRCULATING MEMORY, EACH OF SAID INTERMEDIATE STORAGE STAGES COMPRISING A PLURALITY OF LIKE PERIODIC MEMORIES OF CAPACITY M/N, WHERE N AND M/N ARE POSITIVE INTEGERS. 